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To identify an unknown orchid

January 10, 2011

The orchids are spectacular in morphology and the man-made varieties are often vibrant in colours.

As the scientific consultant for Dokmai Garden I often get the question how to take care of orchids, but that entirely depends on the species. If they all had the same requirements, there would only be one species adapted to one situation, but currently there are 22 500 species and 779 genera known in the world (Mabberley 2008). Since gardeners love to produce new colour varieties and hybrids (crosses of species), the actual number of varieties is almost uncountable. As to the native Thai species, we recently created the Orchid Ark.

Advice number 1: only buy an orchid with a name tag, not a vernacular name (it is as informative as ‘Bob’), but a scientific name (it is even more informative than a social security number). Also, traders who do not use scientific names are usually uneducated thieves who steal orchids from the forest, while serious dealers base their production on plants from cultivation. Do not be cheap, feeling happy you saved 50 Baht buying from a thief, but be a proud gentleman or gentlewoman trying to protect the forest by ignoring the illegal market. Sometimes the scientific name given by a vendor is correct, but old, and therefore not included in your orchid book. You may therefore have to search for synonyms. The internet orchid species photo encyclopedia is a good resource in that case.

Advice number 2: do not lose the scientific name. Store it in the computer, replace the tag if the name tag is lost. Make a map of your tree where orchids cling. Identifying an orchid to species without flowers is usually impossible.

If you know the name, you can google it and get information about origin and care. No need to buy a book.

Sometimes people give you an anonymous orchid as a present. Where shall you plant it? Will it die in full sun or shade, shall you water it in the dry season or not, will it thrive in a tree or shrivel up and die? To know this you need the name, but it is usually a challenge to identify it.

The first question is whether it is native to Thailand or Southeast Asia at all, and is it man-made or natural? If it is an import it may be impossible to fish out the right species form the sea of 22 500 species, unless you are an orchid specialist with a vast experience, not a botanist in general. However, assuming the orchid is native to Thailand will give you a fair chance. The Queen Sirikit Botanical garden publication (Thai Native Orchids volumes 1 and 2) states there are 1157 wild orchid species and 176 orchid genera in Thailand (2008). This is equal to 10% of all flowering plants in Thailand.

Advice number 3: Get the QSBG books ‘Thai Native Orchids 1 and 2’. They do not contain all species, far from it, but they have a fair sample, and the best feature is that the pictures are large. You can buy these books at Dokmai Garden or QSBG, same price. If you think you have tuned in on the right genus, or even species, google those and compare. Nota bene, this book treats the wild orchids only. The spectacular hybrids and colour varieties are not treated.

Advice number 4: To expand the number of illustrated species, get ‘Wild Orchids of Thailand’ by Nantiya Vaddhanaphuti (2005 or later). This book contains more species, but the pictures are consequently small. Again this will help you identify a native wild orchid, but man-made varieties will be different. This book is available at bookstores downtown.

However, even to biologists and general botanists, browsing a book with illustrations can be a hopeless task if you have no specialised experience. You need some kind of system and guidance.

Advice number 5: Get the book ‘Orchid genera of Thailand, Laos, Cambodia and Vietnam’ by Schuiteman & de Vogel (2000). This is an advanced book using keys to identify an orchid genus. The keys are in my eyes a bit old-fashioned (many parallel options instead of two at a time) and often very technical, so this is a book for somebody with a degree in botany. However, even the layman or curious amateur may want to browse the excellent close-up photographs at the end of the book, illustrating representatives of most orchid genera in Southeast Asia. To learn how to use this book, start backwards, i.e. buy an orchid from this region with a name tag, and then try to follow the keys. This book is for sale at Dokmai Garden.

Advice number six: If you can not find your orchid in any of the books above, try the identification key below. I have spent a lot of time trying to learn the Thai orchid genera. For my own eyes I created a simplified key based on literature, experience from Dokmai Garden, the field and the QSBG herbarium. I have only completed the keys for the terrestrial orchids, for the epiphytic orchids I may need another year as the current recession and the red shirt riots caused a serious decline in visitors to Dokmai Garden, forcing me to direct focus on marketing instead of botany.

Since I have no career to protect I have no interest in accumulating publications, and publishing a book is terribly time-consuming. Therefore I hereby publish a preliminary key to the terrestrial orchid genera of Thailand. Please consider this a modest amateur attempt, not a professional treatment, but it may help you with identifications. I have tried to be pedagogic, but a lot of improvement and corrections will be necessary. Kindly send me a message when you discover a flaw, so I can tune the texts.

Ultimately, knowledge will help protecting the Thai nature, which is my chief goal.

Before using the key, you need to be familiar with a couple of technical terms:

To the left a complete flower of Rhynchostylis gigantea var. vivaphandhul. An orchid flower has three sepals and three petals. The most characteristic feature is the lip, a protruding leaf different from the other five flower leaves. The lip is one of the three petals. The other two petals emanate like erect ears to the left and right of the lip. Behind the three petals are three sepals. In this species two of the sepals look like hanging ears of a zebu cow and the third sepal looks like a hood above the lip.

In the middle of the left flower is a horn-like structure called column. This column is a unique feature of the orchid family, distinguishing it from snapdragons (Scrophulariaceae), mints (Lamiaceae), Aeginetia (Orobanchaceae), Canna (Cannaceae) and gingers (Zingiberaceae) which are often mistaken for orchids by the novise. The column contains the male and the female parts. If you use a needle or small knife blade, you can lift the lid of the top of the column, exposing the yellow pollinia (middle flower). These are the male parts, equivalent to animal sperms. Pollinia are pollen aggregates, while most other flowers have powdery pollen on free anthers. The stigma, the female part, is often a pocket with sticky fluid found below the column apex.


The three orchid sepals as seen from behind the flower. Two of the petals are seen behind the sepals. The third petal, the lip, has been removed.

The orchid flower seen from the side. The flower is attached to a flowering stalk, here seen as a whitish bent structure. Below the stalk is the spur, in this case a sac-like structure formed by the rear end of the lip. Presence, direction, shape and interior morphology of the spur may be important for identification. The spur usually produces sugary fluids to attract pollinating insects. A fragrance unique to each species, sometimes not detectable by humans, may appeal to a limited group of pollinators only.

In this picture the lip has been removed, and we look at the orchid flower from below. I lifted out the pollinia which you can see as yellow eye-like structures on top of the column. The mouth-like structure below the yellow pollinia is the stigma, the female part. It may have different morphology in different genera.

The presence of a viscidium or not is also of importance to identification. In this case the pollinia have been detached and the translucent and sticky viscidium is visible at the base of the pollinia stipe. The purpose of the viscidium is to attach to a special pollinator and then be transported to another flower’s stigma for fertilization and consequent seed production. The location of pollinia and stigma are usually adapted to the shape of a certain insect pollinator, for precise matching like in the docking of two space crafts. If the pollinator is extinct, the orchid may no longer reproduce.

A pseudobulb , in this case in Dendrobium chrysotoxum, is an enlargement of the stem and the orchid’s nutrient storage organ. Presence and morphology has importance for identification.

Key to Thai ground (terrestrial) orchid genera

You select one of two options each time, and then proceed to the next pair of options as indicated by a number. For instance, below you start by considering whether your ground orchid has leaves or not at the time of flowering. If it has leaves, you continue to number 16, otherwise you go to 2 where two new alternatives are presented. (Numbers in parentheses after a genus name refer to the number of known Thai species within the genus.) Once you get the genus name, compare with pictures in a book or google it.

1. Orchid without leaves at the time of blossom……2

1. Orchid with leaves at the time of blossom………16

2. The three sepals and the two petals and the lip-petal are all fused together….3

2. Sepals and petals free….5

3. Side (lateral) sepals almost free from the petals………..4

3. Side (lateral) sepals largely fused with the petals…….Gastrodia (2)

4. Column with long projections on either side of the anther (stelidia)…..Didymoplexiella (2)

4. Column without such projections……… Didymoplexis pallens (1)

5. Lip with spur………..6

5. Lip without spur………8

6. Lip with a cystlike swelling on each side of the spur…….Cystorchis (1).

6. Lip without such swellings………7

7. Flowers stiff with spreading sepals & petals………………..  Eulophia (13)

7. Flowers fragile and bell-shaped, whitish-yellowish………..Epipogium roseum (1)

8. Flower with a collar-like structure at the base…….Lecanorchis (2)

8. Flower without such a structure……9

9. Flower with mealy sepals…….Cyrtosia (3)

9. Flower without such structures……10.

10. Pollinia 8, flower pinkish, in fire prone lowlands….Pachystoma pubescens (1)

10. Pollinia less than 8………….11.

11. Pollinia mealy……….12

11. Pollinia solid or grainy (sectile)…….13

12. Lip mobile, flower greenish, growing in lime stone cracks…….Thaia saprophytica (1)

12. Lip not mobile, flower whitish, brownish with violet markings………….Aphyllorchis (4)

13. Flower with lip pointing downwards (resupinate)…….14

13. Flower not resupinate, white-pink, evergreen forests……..Chamaegastrodia poilanei (1)

14. Lip with 2 keels in the basal half…………Cymbidium (19)

14. Lip different……….15

15. Flower snow-white with brownish markings on lip. Didymoplexiopsis khiriwongensis (1)

15. Flower different…………………………..15a.

15a. Flower greenish, roundish leaves after blossom……..Nervilia (9)

15a. Flower showy pink or white………………………….15b

15b. More than 2 flowers, pollinia 2……………….Stereosandra javanica (1)

15b. 1-2 flowered, pollinia 4……………………….Pleione (2)

Ground orchid with leaves at the time of blossom

16. Lip slipper-shaped………Paphiopedilum (14)

16. Lip not slipper shaped………….17

17. Flowers urnlike, pollinia 8, fleshy pseudobulbs…………..Acanthephippium (3).

17. Flowers not urnlike……….18

18. Single green flower with prominent green veins……….Claderia viridiflora (1)

18. Different……19

19. Lip is similar to the petals……………………..Apostasia (3)

19. Lip different from the petals…..20

20. Column with 3 fertile anthers…………..Neuwiedia (2)

20. Column with less anthers…….21

21. Flowers turn bluish when bruised…..22

21. Flowers do not turn bluish when bruised…..24

22. Lip almost free from the column, not showy flower…Cephalantheropsis obcordata (1)

22. Lip fused with the column, often showy flowers………23

23. Viscidium present………Calanthe (16)

23. Viscidium absent…………Phaius (6)

24. Leaves grass-like, flower pink with purple lip…..Arundina graminifolia (1)

24. Leaves grass-like or not, flower with other colour combinations……..25

25. Plant without pseudobulbs, shoot with 3 or more leaves……………………….26

25. Plant with pseudobulbs, or, if without, only 1-2 leaves……………..56

26. Leaves zig-zag in transection………..27

26. Leaves different………..31

27. Pollinia 8…………………Bletilla sinensis (1)

27. Pollinia 2-4………….28

28. Pollinia 4………..Plocoglottis (5)

28. Pollinia 2……………….29

29. Pollinia mealy…………..Epipactis flava (1)

29. Pollinia grainy (sectile)…….30

30. Lip without a spur, tall plant with white flowers…….Corymborkis veratrifolia (1).

30. Lip with a spur or strongly concave………Tropidia (3).

31. Lip with a spur……   32.

31. Lip without a spur…….42

32. Pollinia covered by a cap……33.

32. Pollinia 2, not covered……37

33. Two drumstick-like glands inside the spur……….Vrydagzynea (3).

33. No such glands………34

34. Lip with two hairy patches…….35

34. Lip without two hairy patches…………….36

35. Stigma lobes separated, often ornamented leaves………..Anoectochilus (11)

35. Stigma lobes not separated, more plain leaves……………Pristiglottis (1)

36. Spur inside with warts……………Herpysma longicaulis (1)

36. Spur inside smooth……………….Erythrodes (2)

37. The leaf closest to the flower (bract) is longer than the flower………..Brachycorythis (5)

37. Leaf shorter………38

38. Stigma with 2 widely separated stalked lobes….Habenaria (38)

38. Stigma different…..39

39. Stigma with 2 cushion-shaped lobes…….40

39. Stigma concave……….41

40. Stigma with 2 closely spaced cushion-shaped lobes, showy flower….Pecteilis (3).

40. Stigma with 2 widely separated cushion-shaped lobes, small flower…… Peristylis (12)

41. White or pink flower ………41b

41. Green flower…………….Platanthera (2)

41b Stigma divided into 2 patches. Uniformely green leaf…….. Amitostigma (1)

41b Stigma V-shaped. Variegated leaf………….Hemipilia calophylla (1)

42. Flowers with lip pointing upwards (=not resupinate)……..43

42. Flowers with lip pointing downwards (=resupinate) or sideways……..45

43. Pollinia mealy, leaves long-stalked…….Cryptostylis (1)

43. Pollinia not mealy, leaves not or short-stalked ……44

44. Pollinia solid, flower widely open, leaves plicate…………….Malaxis s.lat. (21+1+1+1)

44. Pollinia grainy (sectile), flower not widely open,leaves not plicate…….Hetaeria (7)

45. Lip pointing sideways, leaves with a whitish-pinkish  mid-vein………..Rhomboda (2)

45. Lip pointing downwards, leaves may be ornamented………46

46. Pollinia mealy……47

46. Pollinia grainy (sectile)…….48

47. Flowers yellow, arranged on one side, 1.5 cm or larger…….Epipactis flava (1)

47. Flowers white or pink, arranged in a spiral…..Spiranthes sinensis (1)

48. Very small green flower with three lobes (midlobe very small)…Herminium lanceum (1)

48. Lip with 1-2 lobes………49

49. Flower dominated by the bilobed & fringed lip. Rhizome swollen………….Cheirostylis (8)

49. Plant different……50

50. Twisted asymmetrical flowers, dark leaves with coloured veins………Ludisia discolor (1)

50. Plant different……..51

51. Lip with a single patch of hairs……Goodyera (6) or 7?

51. Lip with no or two patches of hair…..52

52. Lip shaped like a pouch…….. Hylophila lanceolata (1) (not in QSBG list)

52. Lip different………53.

53. Lip with two hairy patches……..54

53. Lip different……..55

54. Stigma lobes separated, often ornamented leaves………..Anoectochilus (11)

54. Stigma lobes not separated, more plain leaves……………Pristiglottis (1) or 2?

55. Stigma lobes raised. Plant very small……..Myrmechis (1)

55. Stigma lobes not raised…………………..Zeuxine (9)

56. Lip without spur, but the two side (lateral) sepals spurred…..…Disperis (2)

56. Sepals without spurs………..57

57. One roundish leaf with silvery veins, one pitcher-like flower, 4 pollinia……Corybas (1)

57. Different……………………58

58. Lip 3-lobed, side lobes with antenna-like appendages. Flower showy……..Doritis (7)

58. Lip without sidelobes, or sidelobes without antenna-like appendages………..59

59. Spur present……..60

59. Spur absent………. 64

60. Lip mobile, flowers yellow…………..Chrysoglossum ornatum (1)

60. Lip not mobile………….61

61. Lip pointing upwards (not resupinate)……Nephelaphyllum (2)

61. Lip pointing downwards (resupinate)………………..62

62. Pollinia 8…………………Tainia (7)

62. Pollinia 2…………………..63

63. Viscidium absent. Flower assymetrical…………………Collabium (1)

63. Viscidium present. Flower symetrical…………………..Eulophia (13)

64. Pollinia 4…………………………65

64. Pollinia 2 or 8……………………69

65. Lip pointing upwards (not resupinate)…………….Anthogonium gracile (1)

65. Lip pointing downwards (resupinate) ……………66.

66. Column flattened…………………….Coelogyne (30)

66. Column not flattened………………….67.

67. Lip snaps upwards when touched………………Plocoglottis (5)

67. Lip not sensitive to touching………….68

68. Flower maximum 1 cm with lip abruptly bent downwards like an “L”……….Liparis (30)

68. Flower over 1 cm without an L-shaped lip………….Cremastra appendiculata (1)

69. Pollinia 2, flowers facing the ground……………………Geodorum (7)

69. Pollinia 8, flowers facing other directions……………………70

70. Flower stalk without hairs (glabrous)………..71

70. Flower stalk finely hairy………………….73

71. Lip with two fleshy outgrowths (callosities) forming a “v”….Spathoglottis (5)

71. Lip with 2-3 wavy crests…………….72.

72. Heart-shaped leaves without a stem (petiole)………Mischobulbum (2)

72. Leaves not heart-shaped, leaf stem (petiole) long……Tainia (7)

73. Column finely hairy, brownish petals……………..Ipsea thailandica (1)

73. Column not hairy, striped petals……………….Eriodes barbata (1)

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2 Comments leave one →
  1. January 20, 2011 2:23 AM

    Nice in depth article that I know has taken lots of work and sure will progress.

  2. September 22, 2012 10:31 PM

    Thank you for this most valuable resource! I’ve bookmarked the permalink!

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